Pruitt, the Republican attorney general for Oklahoma since 2011, has interacted most directly with the EPA by suing it over what he sees as over-reaching federal regulations. Some scientists have also questioned his fitness to run the environmental agency considering he has publicly stated that he believes the debate over the cause of global warming is “far from settled.”

His nomination to now lead the agency is akin to putting "someone in charge of the Defense Department who doesn't believe we should have a military, or someone in charge of the Transportation Department who doesn't like roads," said Dan Kanninen, a former White House liaison at the EPA.

But Pruitt, 48, appears to pride himself on his work against the EPA, describing himself as a "leading advocate against the EPA’s activist agenda" in his biography on the official Oklahoma state website.

“I am deeply grateful and honored to serve as President-elect Trump’s EPA Administrator,” Pruitt said in in a Trump transition team statement today announcing his selection, which requires Senate approval.

"The American people are tired of seeing billions of dollars drained from our economy due to unnecessary EPA regulations, and I intend to run this agency in a way that fosters both responsible protection of the environment and freedom for American businesses.”

Here is where he falls on some of the issues:

He Believes the Global Warming Debate Is Unsettled

Pruitt co-authored a May op-ed piece for the National Review, a conservative publication, saying "global warming has inspired one of the major policy debates of our time," but "that debate is far from settled."

"Scientists continue to disagree about the degree and extent of global warming and its connection to the actions of mankind," the article reads.

But the vast majority of scientists in this field disagree, according to multiple studies cited by NASA. It says those studies claim 97 percent or more of actively publishing climate scientists agree that “climate-warming trends over the past century are extremely likely due to human activities.”

Rob Young, director of the Program for the Study of Developed Shorelines at Western Carolina University in Cullowhee, North Carolina, told ABC News that it should come as no surprise that Trump's EPA pick has "an anti-regulation" stance, but that shouldn't automatically rule out established science’s conclusion that mankind is contributing to global warming.

"The greatest concern that I have and that a lot of scientists have in response to this is the fact that this individual seems to have an anti-science agenda as well, and one can acknowledge the role that humans are playing in changing the chemistry of our atmosphere and changing the temperature on the planet and still disagree about what you do about it, and that's a policy discussion," Young said.

Oklahoma Joined a Challenge to the EPA’s Clean Power Plan

Pruitt and his office this year helped prepare a lawsuit, which included other states and was led by the West Virginia solicitor general, in which the plaintiffs are fighting the EPA to stop its plan to reduce power plant carbon dioxide emissions (the Clean Power Plan).

"This administration continues to treat states as mere vessels of federal will, abusing and disrespecting the vertical separation of powers defined by our Constitution,” Pruitt said after a day of hearings in the West Virginia v. EPA case in September.

“That is why attorneys general, senators and congressmen from across the country have joined together today to maintain rule of law and checks and balances in this very process. I am committed to ensuring the ultimate payer in this matter is not overlooked – the consumers.”

This position is in keeping with his overarching commitment as Oklahoma attorney general to eliminate what he calls “unwarranted regulation and overreach by the federal government,” according to his biography on the state website.

The case, West Virginia v. EPA, is still open and ongoing in the D.C. Court of Appeals.

Oklahoma’s Own Lawsuit Was Dismissed

Pruitt had filed a similar lawsuit pre-emptively last year trying to stop the EPA from enforcing the same Clean Power Plan, saying it exceeded the agency’s authority and was already doing "irreparable harm" to Oklahoma.

"Whether the State of Oklahoma adopts a state plan to meet EPA’s goals or EPA promulgates a federal implementation plan, the EPA Power Plan forces the State of Oklahoma to undertake substantial legislative, regulatory, planning, and other activities," the suit alleged.

The case was dismissed in July 2015 and the appeal was dismissed in September 2015, according to the court docket.

Pruitt released a statement in May saying the controversial pipeline would "continue to create jobs" and slammed President Obama and his administration for "continu[ing] to interfere with the completion of the pipeline."

"The president’s own State Department has concluded, after years of study, that the pipeline will do little to directly harm the environment or increase greenhouse gas emissions, so his actions to prohibit the pipeline are solely an attempt to place his 'legacy' and political ambition above our country’s ability to move closer to energy independence," Pruitt said in a statement.

He Has Ties to the Oil and Gas Industry

Beyond taking a public stance against the EPA and raising doubts about the scientifically established cause of global warming, Pruitt has financial alliances to the oil and gas industry that trouble some opponents. The connection largely comes from the various oil and natural gas extraction projects that are underway in Oklahoma, which have come under scrutiny amid the rise in fracking and earthquakes in the landlocked state.

While defenders of the projects argue that the increase in earthquakes is unrelated to fracking, Young, of Western Carolina University, says that when water released in the process is forced back into the ground, it frequently plays a major factor in causing earthquakes.

The New York Times reported on Pruitt's ties to oil and gas in 2014 when it claimed that a letter from Pruitt to the EPA that was actually written by lawyers for Devon Energy, an oil and gas company based in Oklahoma.

In response to the Times report, Pruitt provided a statement to Oklahoma station KFOR: "The article did not accurately reflect what motivates my service and how we seek to make decisions on advancing these cases," the statement read. "Our responsibility is to protect Oklahoma’s interest when any federal agency seeks to displace the authority granted to the state under federal law. This administration has given us plenty of opportunity to litigate those matters in regards to energy, the environment, and health care and that is what is driving us, nothing more or nothing less."

"It should come as no surprise that I am working diligently with Oklahoma energy companies, the people of Oklahoma and the majority of attorneys general to fight the unlawful overreach of the EPA and other federal agencies," the letter read.

Kanninen, who has worked in several Democratic political positions, including his time at the Obama White House and working as a Wisconsin state director for Obama's campaign during the 2008 election, said Pruitt "is someone who has been in the belly of the oil and gas industry; that’s where he comes from."

"He's well known as an antagonist to the environmental community. Someone who's repeatedly taken the side of the oil and gas industry," Kanninen said.

Campaign finance records show that Pruitt received $5,000 in contributions from the Koch Industries PAC during his 2010 campaign for attorney general, and BP donated $500.

He also received contributions from the Marathon Oil Company Employee's PAC for $1,000, the Chevron Employees PAC for $1,000 and the OGE Energy Corp. Employee's PAC for $3,500, according to Oklahoma state records.

Trump, however, praised Pruitt's work and said in a statement announcing his pick that Pruitt would "reverse this trend" of how he alleges the EPA spends "taxpayer dollars on an out-of-control anti-energy agenda that has destroyed millions of jobs, while also undermining our incredible farmers and many other businesses and industries at every turn."